William w



UNITEDv STATES PATENT OFFICE.

VILLIAM IV. DOOLITTLE, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE CRANE COMPANY, OF SAME PLACE.

BACK- PRESSU RE VALVE.

SPECIFICATION forming part of Letters Patent No. 486,950, dated November 29, 1892.

Application filed July 9, 1892. Serial No. 439,483. (No model.) l

To @ZZ whom it may con/cern.- tending inward from the plate into the cen- Beit known that I, WILLIAMV. DOOLITTLE, tral chamber of the casing. The stud is bored a citizen of the United States, residing at Chito provide a bearing for a shaft D, which is cago, in the county of Cook and State of Illimounted therein,beingextended inward from l 5 nois, have invented a certain new and useful the outside and through the stud. A stuffing- 55 Improvementin Back-Pressure Valves, which\' box is provided in the latter, if required. At is fully set forth in the following specication, the inner end of the shaft, projecting from the reference being had to the accompanying inner end of the stud, there is a short crankdrawings, in whicl1` arm E, fixed upon a shaft by means of a set- Io Figure 1 represents a side elevation of a screw e or any other suitable device. The 6o valve embodying my invention; Fig. 2, a secouter or free end of this crank-arm' is contion of the same, taken on the line 2 2 of Fig. nected by a link-rod F to the valve B, being 1; Fig. 3, a similar section taken on the line pivoted to each at its respective ends, as seen 3 3 of Fig. 2, and Fig. 4 a bottom plan of the in Fig. 3. As shown by the drawings, the

15 valve itself detached. outer end of the crank-arm is forked, and the 65 Myinvention relatesto back-pressure valves upper end of the link is pivoted between the which are intended to be held in closed positwo arms e of the fork, the upper end fof the tion by a weighted lever; and the improvelink-rod extending upward slightly above the ment consists in constructing and arranging pivot and past the center of the solid portion zo the parts so that when the valve is closed the of the crank-arm, as seen in Fig. 3. A lever 7o weighted lever will always hang vertically, G is secured by any suitable device on the thus obviating the necessity of stops or other outer end of the shaft D outside of the casing. like devices. This lever is preferably bent, being provided I will now describe in detail the construcwith a long arm g and a short arm g', stand- 2 5 tion and operation of a valve device embodying at an angle to the fork, and the lever is 75 ing my improvement in a practical way, and secured to the shaft at the angle of these two will then more definitely specify in the claims arms, as seen in Fig. l. the particular improvements which I believe Now the parts described above are so conto be new and wish to secure by Letters Patstructed and arranged relatively to each other 3o ent. that when the lever stands with its long arm 8o In the drawings, A represents a valve-case depending vertically from the shaft, as seen of any ordinary construction. As here shown in Fig. l, the valve always will be closed. A it is of general circular form provided with weight H is applied to the long arm of the leround apertures a and a at the upper and ver and obviously will have a tendency to 3 5 lower ends of the casing, respectively, while bring this arm of the lever to this vertical po-` 85 between the two there is an enlargement to sition, and, as seen in Fig. 1, this weight is provide a chamber a2 of somewhat-larger cirmade adjustable on the arm and secured in cumference. The valve B is of the piston type any position by means of a set-screw h or any and is fitted within the lower opening a of other suitable device.

4o the case. The valve isnot seated in the usual In operation it is obvious under all ordi- 9o sensewithin the case, but it is cup-shaped, nary circumstances that the long arm of the and its exterior or cylindrical rim b is prolever will be returned to its vertical position vided with a series of openings or slots b', automatically bythe action of its weight,and whereby passages to the central chamber in in this position it will also keep the valve 45 the casing are opened or closed, according to closed. Whenever4 the pressure upon the 95 the position of the valve. At one side of the valve becomes excessive, however, and so recasing there is an opening a3, and a head C, quires relief, the valve will be lifted against adapted to close this opening, is properly sethe action of the weighted lever until pascured to the casing, as seen in Fig. 2. This sages are made for the escape of steam into 5o head is provided with an arm or stud c, exthe chamber above. As the pressure is thus roo diminished the weighted lever will automatically drop into a vertical position again, thus closing the valve. Owing to this arrangement and operation of the Weighted lever, there is no necessity for any special device for stopping the lever at any point or at the point desired. It takes and keeps the position required for holding the valve closed naturally and without any stop device and moves from this perpendicular position with the change of the pressure of steam on the valve.

If at any time it is desired to hold the valve open, the weight is shifted from the long arm to the short arm of the lever, when the latter will operate to hold the valve in an elevated or open position. In carrying out this improvement I arrange the lever-shaft in a vertical plane as near to the vertical plane of the two pivots of the link-rod as possible and give room fortheworkingof the parts. Thisarrangement is such that the joints form a kind of toggle in which the joints are approximately in line when the valve is fully closed, as seen in Fig. 3. Now in this position theleverage of the link upon the shaft is least, andconsequently the weighted lever` is not more readily moved by comparatively-small changes in pressure upon the valve. It will be seen, however, that as soon as the valve moves upward, thereby carrying the link in the same direction, the leverage on the link of the shaft will be increased, but at the same time,theweighted lever beingcarried out from its vertical position by the turning of the shaft, its resistance to such movement of the latter will be increased. These two forces act as a kind of balance to each other and operate to maintain a substantially-uniform resistance to the upward movement of the valve. With this construction, however, it will be impossible to bring the joints directly in line and so close the toggle, when of course the device would be held at rest and inoperative until the toggle is broken. rlhe danger of this accident, however, is obviated by the extension of the upper end of the link, as heretofore described, as this projection will be brought in contact with the hub before the joints are main feature of my invention being the rela- 4 `tive arrangement. of the parts under which the weighted lever always drops to the vertical position to close the valve and retain it in this adjustment.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is-

l. In a back-pressure valve, a piston-valve, in combination with a shaft mounted in the case, a link-rod hinged to one end to the valve and at the other to the shaft eccentrically to the axis thereof, an-d a weighted lever mounted on a fixed shaft outside the case and arranged to close the valve when standing in a vertical position, substantially as described.

2. The valve-case A, in combination with the piston-valve B, freely rocking shaft D, the crank-arm E of the inner end thereof, the link-rod F, hinged, respectively, to the valve and crank-arm and with joints arranged to form a toggle, and the weighted lever G, attached to said shaft,substantiallyas described.

3. The valve-case A, in combination with a piston-val ve B, the freely-rockin g shaft D, the forked crank-arm E, fixed on the inner end thereof, the link-rod F, connecting the valve and crank-arm and extending a little beyond the forked arms of the latter, and the weighted l lever G, all relatively arranged to close the valve and retain it in this adjustment under ordinary pressure by the lever dropping into a vertical position, substantially as described. 4. The valve-case A, provided'with a side opening a3, in combination with the head C to close said opening and provided with a stud c, extending into the casing, the shaft D, mounted in said stud, the piston-valve E, linked eccentrically to thev shaft, and the weighted lever Gr, fitted on the outer end of the shaft, substantially as described.

' WILLIAM W. DOOLITTLE. Witnesses:

R. C. PAGE, t ALoYsIA HELMICH. 

